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<!DOCTYPE HTML PUBLIC "-//W3O//DTD W3 HTML 2.0//EN"><!-- This collection of hypertext pages is Copyright 1995-2005 by Steve Summit. --><!-- Content from the book "C Programming FAQs: Frequently Asked Questions" --><!-- (Addison-Wesley, 1995, ISBN 0-201-84519-9) is made available here by --><!-- permission of the author and the publisher as a service to the community. --><!-- It is intended to complement the use of the published text --><!-- and is protected by international copyright laws. --><!-- The on-line content may be accessed freely for personal use --><!-- but may not be published or retransmitted without explicit permission. --><!-- --><!-- this page built Sat Dec 24 21:47:45 2005 by faqproc version 2.7 --><!-- from source file malloc.sgml dated Wed Dec 21 13:50:44 2005 --><!-- corresponding to FAQ list version 4.0 --><html><!-- Mirrored from c-faq.com/malloc/useafterfree.html by HTTrack Website Copier/3.x [XR&CO'2008], Sat, 14 Mar 2009 07:58:51 GMT --><head><meta name=GENERATOR content="faqproc"><title>Question 7.20</title><link href="noscale.html" rev=precedes><link href="ptrafterfree.html" rel=precedes><link href="index.html" rev=subdocument></head><body bgcolor="#ffffff"><a href="noscale.html" rev=precedes><img src="../images/buttonleft.gif" alt="prev"></a><a href="index.html" rev=subdocument><img src="../images/buttonup.gif" alt="up"></a><a href="ptrafterfree.html" rel=precedes><img src="../images/buttonright.gif" alt="next"></a> <a href="../index-2.html"><img src="../images/buttontop.gif" alt="top/contents"></a><a href="../search.html"><img src="../images/buttonsrch.gif" alt="search"></a><hr><p><!-- qbegin --><h1>comp.lang.c FAQ list<font color=blue>·</font><!-- qtag -->Question 7.20</h1><p><font face=Helvetica size=8 color=blue><b>Q:</b></font>You can't use dynamically-allocated memory after you free it, can you?</p><p><hr><p><font face=Helvetica size=8 color=blue><b>A:</b></font>No.Some earlydocumentationfor <TT>malloc</TT> stated that the contents of freedmemorywere``left undisturbed,''butthis ill-advised guaranteewas neveruniversal and is not requiredby the C Standard.</p><p>Few programmers would use the contents of freed memorydeliberately, but it is easy to do so accidentally.Consider the following (correct) code for freeing a singly-linkedlist:<pre> struct list *listp, *nextp; for(listp = base; listp != NULL; listp = nextp) { nextp = listp->next; free(listp); }</pre>and notice what would happenif the more-obvious loop iterationexpression <TT>listp = listp->next</TT>were used,without the temporary <TT>nextp</TT> pointer.</p><p>References:K&R2 Sec. 7.8.5 p. 167<br>ISO Sec. 7.10.3<br>Rationale Sec. 4.10.3.2<br>H&S Sec. 16.2 p. 387<br>CT&P Sec. 7.10 p. 95<br></p><!-- aend --><p><hr><a href="noscale.html" rev=precedes><img src="../images/buttonleft.gif" alt="prev"></a><a href="index.html" rev=subdocument><img src="../images/buttonup.gif" alt="up"></a><a href="ptrafterfree.html" rel=precedes><img src="../images/buttonright.gif" alt="next"></a> <a href="../questions.html"><img src="../images/buttontop.gif" alt="contents"></a><a href="../search.html"><img src="../images/buttonsrch.gif" alt="search"></a><br><!-- lastfooter --><a href="../about.html">about this FAQ list</a> <a href="../eskimo.html">about eskimo</a> <a href="../search.html">search</a> <a href="../feedback.html">feedback</a> <a href="copyright.html">copyright</a><p>Hosted by<a href="http://www.eskimo.com/"><img src="../../www.eskimo.com/img/link/eskitiny.gif" alt="Eskimo North"></a></body><!-- Mirrored from c-faq.com/malloc/useafterfree.html by HTTrack Website Copier/3.x [XR&CO'2008], Sat, 14 Mar 2009 07:58:51 GMT --></html>⌨️ 快捷键说明
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